The **AD7989-1BCPZ-R2** is a high-performance, 18-bit, successive approximation register (SAR) Analog-to-Digital Converter (ADC). It is designed for low-power, high-precision applications. --- ### ## Technical Specifications The following table summarizes the primary electrical characteristics of the AD7989-1: | Parameter | Specification | | :--- | :--- | | **Resolution** | 18 Bits | | **Throughput Rate** | 100 kSPS (Kilo Samples Per Second) | | **Interface** | SPI-compatible Serial Interface | | **Signal-to-Noise Ratio (SNR)** | 98 dB (typical) | | **Total Harmonic Distortion (THD)** | -114 dB (typical) | | **Power Consumption** | 400 µW (at 100 kSPS) | | **Package** | 10-Lead LFCSP (3mm x 3mm) | | **Input Type** | Pseudo-differential | --- ### ### Key Internal Components & Features 1. **SAR Core**: Unlike Delta-Sigma ADCs, the SAR architecture allows for zero-latency conversion, making it ideal for multiplexed channels or high-speed control loops. 2. **Internal Capacitor DAC**: Used during the conversion process to perform a binary search for the analog input voltage level. 3. **Low Power Architecture**: The device scales its power consumption linearly with the sample rate. When the ADC is not converting, it automatically powers down, making it perfect for battery-operated devices. 4. **Reference Input**: It requires an external reference voltage (VREF). This allows the user to define the full-scale input range (typically between 2.5V and 5V). --- ### ### Pin Functionality (Selected) | Pin Name | Description | | :--- | :--- | | **IN+ / IN-** | Differential analog inputs. | | **REF** | Reference input voltage; determines the dynamic range. | | **VIO** | Digital interface supply (1.8V to 5V logic compatibility). | | **SDO** | Serial Data Output (SPI data). | | **CNV** | Convert Start Input; rising edge initiates the conversion. | --- ### ### Typical Application Circuit The AD7989 is often paired with a precision op-amp (like the ADA4841) to drive the analog inputs and a low-noise voltage reference (like the ADR45xx). ```c // Pseudo-code representation of reading from AD7989 via SPI uint32_t read_adc() { uint32_t raw_data = 0; digitalWrite(CNV_PIN, HIGH); // Start conversion delay_microseconds(10); // Wait for conversion time (tCONV) digitalWrite(CNV_PIN, LOW); // Prepare for SPI read raw_data = SPI.transfer24(0x00); // Read 18-24 bits return raw_data >> 6; // Align bits for 18-bit result } ``` ---